Erkki Hiltunen

Nutrient removal and biodiesel production by integration of freshwater algae cultivation with piggery wastewater treatment.

An integrated approach, which combined freshwater microalgae Chlorella zofingiensis cultivation with piggery wastewater treatment, was investigated in the present study. The characteristics of algal growth, lipid and biodiesel production, and nutrient removal were examined by using tubular bubble column photobioreactors to cultivate C. zofingiensis in piggery wastewater with six different concentrations. Pollutants in piggery wastewater were efficiently removed among all the treatments. The specific growth rate and biomass productivity were different among all the cultures. As the initial nutrient concentration increased, the lipid content of C. zofingiensis decreased. The differences in lipid and biodiesel productivity of C. zofingiensis among all the treatments mainly resulted from the differences in biomass productivity. It is worthy of note that the diluted piggery wastewater with 1900 mg L(-1) COD provided an optimal nutrient concentration for C. zofingiensis cultivation, where the advantageous nutrient removal and the highest productivities of biomass, lipid and biodiesel were presented.

Scale-up potential of cultivating Chlorella zofingiensis in piggery wastewater for biodiesel production

Scale-up potential of cultivating Chlorella zofingiensis in piggery wastewater for simultaneous wastewater treatment and biodiesel production was tested. The cultivation of C. zofingiensis with autoclaved wastewater and NaClO-pretreated wastewater, cultivation of algae indoors and outdoors, and stability of semi-continuous feeding operation were examined. The results showed that C. zofingiensis cultivated in piggery wastewater pretreated by autoclaving and NaClO had no evident difference in the performance of nutrient removal, algal growth and biodiesel production. The outdoor cultivation experiments indicated that C. zofingiensis was able to adapt and grow well outdoors. The semi-continuous feeding operation by replacing 50% of algae culture with fresh wastewater every 1.5 days could provide a stable net biomass productivity of 1.314 g L(-1) day(-1). These findings in this study can prove that it is greatly possible to amplify the cultivation of C. zofingiensis in piggery wastewater for nutrient removal and biodiesel production.

Recycling harvest water to cultivate Chlorella zofingiensis under nutrient limitation for biodiesel production

Harvest water recycling for Chlorella zofingiensis re-cultivation under nutrient limitation was investigated. Using 100% harvest water, four cultures were prepared: Full medium, P-limited medium, N-limited medium and N- and P-limited medium, while another full medium was also prepared using 50% harvest water. The results showed that the specific growth rate and biomass productivity ranged from 0.289 to 0.403 day(-1) and 86.30 to 266.66 mg L(-1) day(-1), respectively. Nutrient-limited cultures witnessed much higher lipid content (41.21-46.21% of dry weight) than nutrient-full cultures (26% of dry weight). The N- and P-limited medium observed the highest FAME yield at 10.95% of dry weight, while the N-limited culture and P-limited culture shared the highest biodiesel productivity at 20.66 and 19.91 mg L(-1) day(-1), respectively. The experiment on harvest water recycling times demonstrated that 100% of the harvest water could be recycled twice with the addition of sufficient nutrients.

Energy diversification in Finland: achievements and potential of renewable energy development

Finland was an early adopter of several alternative energy technologies, particularly in biomass and hydropower energy for many years. The main policy in the Finnish energy and climate sectors is to increase the exploitation of renewable energy sources while reducing CO2 emissions. Meanwhile, a successful energy policy should achieve three conflicting objectives: clean, cheap, and secure energy. The development of renewables in Finland has lagged that of other EU countries, particularly in fields such as wind power in recent years. This article discusses about the history, current status, and potentials of the major renewable and local energy in order of utilisation in Finland. It is seen that the major contributors to replacing carbon-based fuels are likely to be biomass and wind power, with geothermal and solar energy sources to play a lesser role.

Comparison of vertical-flow constructed wetlands with and without supplementary aeration treating decentralized domestic wastewater

Constructed wetlands (CWs) are efficient in reducing excessive contamination from wastewaters. However, oxygen inside CW beds is frequently low especially when substrate clogging problems appear after long-term operation, and this may become a limited factor for the treatment of wastewaters. Aimed at dealing with the issue of a low oxygen content in CW systems, two laboratory-scale vertical-flow constructed wetlands (VFCWs) with and without an aeration device (called VFCW-a and VFCW-c, respectively) were designed in this study to test the contribution of supplementary aeration to the treatment of decentralized domestic wastewater. Results showed that under the intermittent operation of about 45 days, two VFCW units were successfully started up by using activated sludge as seed sludge. Compared to VFCW-c, VFCW-a had a better resistance ability to organic shock loads and its removal function could be effectively recovered within a short period after the introduction of organic shock loads. Under intermittent operation with a 12 h idling time, the ideal hydraulic retention time (HRT) of VFCW-a was 42 h, about 6 h shorter than that of VFCW-c. Likewise, under intermittent operation with 42 h HRT, the ideal idling time of VFCW-a was 12 h, still about 6 h shorter than that of VFCW-c. Under intermittent operation with HRT-42 h and an idling time of 12 h, SS, COD, TN and TP removal efficiencies in VFCW-a could reach 81.2%, 85%, 89.9% and 77.9%, respectively. The VFCW unit with supplementary aeration is an efficient innovation for the treatment of decentralized domestic wastewater.

Oil production from pilot-scale microalgae cultivation: An economics evaluation

ABSTRACT Of the potential sources of renewables, the most promising one is microalgae, which are viewed as a biofuel feedstock and technological solution for CO2 sequestration. Among microalgae-derived biofuels, biodiesel is one of the best application choices since microalgae have substantial amounts of oils. Nonetheless, microalgal biodiesel production is still in its infancy, since there is no commercial production on a large scale. The economic data and evaluation related to microalgal biodiesel production are incomplete and out of date, although lots of technological research has been carried out. This article demonstrates the pilot scale cultivation of microalgae in photobioreactors and evaluates the economics of producing oil from microalgae, including net energy ratio and cost-effectiveness evaluation. The contribution of this article lies in the presentation of an updated analysis of economic conditions for pilot scale microalgal oil production, which can provide the direction for future development of this important biofuel process.

The first generation biodiesel: The effects of raw material on physical properties, oxidation stability and emissions

The aim of this study was to compare oxidation stability, emissions during engine tests and fuel properties of biodiesels. The biodiesels were produced from different raw materials using the transesterification process. The raw materials used were: salmon oil, fox fat, rainbow trout oil, rapeseed oil and linseed oil. The engine tests showed differences in emissions with different biodiesels. The fatty acid profiles were measured and their effect on oxidation stability and other fuel properties were noticeable. The effect of synthetic antioxidant was also measured for different biodiesels. The oxidation stability increase was related to the raw material used to produce the fuel. The oxidation stability of biodiesel blends was measured. The oxidation stability of the blended fuel increased when biodiesel with a higher oxidation stability level was introduced. These measurements indicate that oxidation stability can be enhanced with antioxidants and by blending diesel fuel or other biodiesels together.

Using magnetic materials to harvest microalgal biomass: evaluation of harvesting and detachment efficiency

ABSTRACT Using naked iron oxide (Fe3O4) and yttrium iron oxide (Y3Fe5O12) nanoparticles as flocculants, the harvesting efficiency of Chlorella vulgaris biomass was investigated. The harvesting process includes two steps, which are the separation of microalgae from the culture solution with the magnetic nanoparticles and then the separation of the algae from the magnetic nanoparticles. The optimal dosages and pH values for the magnetic harvesting of microalgal biomass were determined. Results showed that Y3Fe5O12 nanoparticles were more efficient in microalgal biomass harvesting than Fe3O4 nanoparticles. In an effort to achieve more than 90% of harvesting efficiency, optimal dosages for Fe3O4 and Y3Fe5O12 to harvest microalgal biomass were 10 and 2.5 g/L, while the appropriate pH values were 6.2 and 7.3, respectively. The harvesting efficiency of Fe3O4 and Y3Fe5O12 nanoparticles increased as the pH value decreased. The experimental results also showed that under a higher pH value Fe3O4 nanoparticles were much easier to be separated from the flocs than Y3Fe5O12. 62.9% of Fe3O4 nanoparticles could be de-attached from the aggregates, when the floc pH value reached 12.3.

Results of an Off-Road Diesel Engine Driven With Different Animal Fat Based Biofuels

The demand for increased use of biofuels in both on- and off-road diesel engines is growing. The carbon dioxide emissions must be reduced, but the increase in the petroleum prices and possible shortage of crude oil also promote the interest in biofuels. Simultaneously, exhaust pollutants of diesel engines have to be drastically reduced. The nitrogen oxides (NOx ) and particulate matter (PM) form the main challenge for diesel exhaust cleaning. Despite the emissions reduction, the fuel economy of the engines should be kept at a sufficient level to also prevent the CO2 increase. In the present study, a turbocharged, inter-cooled direct-injection off-road diesel engine was driven with two animal fat based bio-fuels, namely steelhead (or rainbow trout) methyl ester (StME) and crude steelhead oil (StO). Crude or neat biofuels are also of interest since medium-speed engines are able to burn unrefined bio-oils. A vegetable oil based fuel, canola oil methyl ester (RME) served as the main reference biofuel. The baseline results were measured with commercial low-sulfur diesel fuel oil (DFO). The main aim of the project was to clarify how the waste-derived animal fat based biofuels are suited to engine use. The performance and emissions characteristics of the engine were determined. In addition to regulated emissions, the particle size distributions were also examined. The results showed that the studied animal fat derived ester was very suitable for the off-road test engine. NOx increased but hydrocarbons (HC), smoke, and PM mass decreased (by up to 60%) while thermal efficiency and carbon monoxide (CO) remained approximately unchanged. The particle number emissions were competitive relative to DFO. Raw fish oil StO reduced HC emissions but increased NOx and particle mass and number emissions. CO and smoke behaved ambiguously, so further investigation is needed for this fuel.Copyright

Environmental Sustainability of Microalgae Production as a Biofuel Source

The issues of energy shortage, global warming and climate change have led to an increased interest in new energy sector, such as microalgae-based biofuels. There are many advantages to produce microalgae as a biofuel feedstock, for instance, high photosynthesis efficiency and uncompetition with traditional agriculture on farmlands. Benefiting from current culturing technologies, such as open ponds and photobioreactors, commercial microalgae farming (e.g., Earthrise) is booming. In this regard, identifying the main environmental benefits associated with microalgae production is pretty important to support this promising industry. Although there are many researches on microalgae production, published information available on the sustainably environmental benefits is fragmented. The aims of this paper are to investigate and analyze environmental benefits related with microalgae biomass production for biofuel usage from sustainability perspective, systematically and explicitly, including water resource, land, nutrient, greenhouse gases and genetic modification dimensions.